GILROY — Police have identified a fourth suspect in the slaying of a Gilroy man last month, officials said.

San Jose resident Gerardo Cisneros, 20, was in custody in Alameda County on an unrelated matter, police said, when they served a warrant for his arrest, and he was moved to Santa Clara County Jail.

According to police, one suspect is still outstanding in the killing of 56-year-old Robert Joseph Heiser on Feb. 16 — 17-year-old Isabella Chaidez.

Two other suspects were already in custody in connection with Heiser’s death before Cisneros’ arrest.

Detectives continue to investigate the incident, and anyone with information relating to Heiser’s death or the whereabouts of Chaidez can call homicide Detective Eric Cryar at 408-846-0330 or 408-846-0350.

In addition to evacuating 10 neighboring homes, deputies restricted pedestrian and vehicle traffic in the area while the sheriff's office bomb squad "safely disposed" of the explosives, officials said.